T, any ditch can be considered an Intermittent Stream during a rain event, and we all know the EPA would love control over every drop of rain...in fact, they are trying to pass those rules right now to gain control over all water above, on or below the ground inside the US borders. My question is, has the COE or EPA actually declared they have jurisdiction over the area in question? Has your state? Your engineering firm may just assume a 404 permit is required, but that permit is often not required at all. Also, mitigation does not always need to be in the form of a cash payment. IF a 404 is needed, the EPA/COE may prefer a shallow "wetlands" type area be built instead of cash....that could be a win win for you.

As far as cattle, the pond can be fenced off from them and water sent to a trough below...or a few goats used instead of cattle....Vegetation control??